Indocyanine Green Angiography - Carver College of Medicine

ICG is used to acquire an angiogram of the choroid. The choroid is the layer of blood vessels and connective tissue between the sclera (white of the eye) and retina. It supplies nutrients to the inner parts of the eye.

Please visit our website for more information on this topic.

A procedure similar to fluorescein angiography, but ICG angiography uses Indocyanine Green dye, which fluoresces in the infra-red (non-visible) light. The infra-red wavelenths have the ability to penetrate the retinal layers making the circulation in deeper layers visible when photographed with an infra-red sensitive camera.

ICG is injected intravenously and flows through the body to reach the choroidal and retinal circulation. Due to its nature ICG stays in the retinal and choroidal vessels, this allows the distinct outlines of the vessels of the choroid to be seen and identified. ICG is sometimes used to complement fluorescein angiography (FA). FA is often referred to retinal angiography while ICG angiography is referred to choroidal angiography.

ICG was first used in [1] but was not brought into the practical clinical setting until .[2]

Case Example:

In the case of a patient with 20/100 vision, the fluorescein angiogram demonstrated leakage of fluorescein dye over a large area near the fovea. Traditional treatment would dictate that the entire area of leakage be treated with laser surgery. The treatment of this lesion would cause an instant decline in vision to 20/400.

The ICG angiography, performed on the same day, reveals a pinpoint leak not visible with fluorescein angiography. Focal treatment based on the ICG angiogram caused an increase in vision from 20/100 to 20/80.

After treatment the laser scar is visible on the color fundus photograph. Both the fluorescein and the ICG angiograms show no leakage of dye demonstrating that the focal treatment was effective.

Photographs by UIHC Opthalmic Imaging Staff

References:

1. Kogure K, Choromokos E. Infrared absorption angiography. J Appl Physiol. ;26(1):154-7.
2. Yannuzzi LA, Slakter JS, Sorenson JA, Guyer DR, Orlock DA. Digital indocyanine green videoangiography and choroidal neovascularization. Retina.;12(3):191-223.

Diagnostic procedure

Choroidal blood flow revealed with indocyanine green angiography

Indocyanine green angiography (ICGA) is a diagnostic procedure used to examine choroidal blood flow and associated pathology. Indocyanine green (ICG) is a water soluble cyanine dye which shows fluorescence in near-infrared (790&#;805 nm) range, with peak spectral absorption of 800-810 nm in blood.[1][2] The near infrared light used in ICGA penetrates ocular pigments such as melanin and xanthophyll, as well as exudates and thin layers of sub-retinal vessels.[3] Age-related macular degeneration is the third main cause of blindness worldwide, and it is the leading cause of blindness in industrialized countries.[4] Indocyanine green angiography is widely used to study choroidal neovascularization in patients with exudative age-related macular degeneration.[5] In nonexudative AMD, ICGA is used in classification of drusen and associated subretinal deposits.[5]

Indications

[

edit

]

Indications for indocyanine green angiography include:

Procedure

[

edit

]

Fundus camera-based indocyanine green angiography techniques and scanning laser ophthalmoscope-based indocyanine green angiography techniques are there.[10] The concentration of indocyanine green dye may vary according to instrument used. For fundus cameras, 25 ml ICG dissolved in 5 ml solvent is used, it may be increased to 50 ml in patients with poorly dilated pupil and high pigmentation.[6] In case of iodine allergy, instead of ICG, iodine-free dye Infracyanine green should be used.[11]

weiqing supply professional and honest service.

To perform test, pupil should be dilated. The dye is injected through the antecubital vein as bolus.[12] Images are taken in several second intervals until the retinal and choroidal circulations are maximally hyperfluorescent.[10] Then for first few minutes, take photos at approximately 30 to 60 second intervals. Pictures taken are classified under three phases:[13]

1. Early phase at 60 seconds: large choroidal arteries and veins are highlighted in this phase.[14]
2. Mid phase at 5&#;15 minutes: in this phase choroidal vasculature become less distinct and more diffuse, and hyperfluorescent lesions appear bright against the fading background.[14]
3. Late phase at 15&#;30 minutes: in this phase hyperfluorescent lesions appear bright against the dark background.[14] The choroidal neovascularization are best detected in this phase.[14]

Advantages over fluorescein angiography

[

edit

]

Indocyanine green angiography has many advantages over commonly used fundus fluorescein angiography (FFA). Because of its protein-binding properties, its leakage from choriocapillaries is less and thus it will remain longer in choroidal vessels compared to fluorescein dye.[1] Choroidal neovascularization is better visualized by ICGA, than fluorescein angiography.[5] The patient toleration is also better compared to FFA.[12]

History

[

edit

]

Physical and physiological properties of indocyanine green dye were first described by Fox and Wood, in .[15] Indocyanine green angiography was developed by Kodak Research Laboratories for determining cardiac output. In , Kogure et al. performed intra-arterial choroidal absorption angiography using indocyanine green dye in monkeys.[16] In the year , using ICGA, Kogure and Choromokos studied cerebral circulation in a dog. In , Hochhimer replaced color film with black and white infrared film. First human ICG angiogram was of carotid artery. First intravenous ICGA in human eye was performed by Flower and Hochheimer in .[12][6] In Hayashi et al. used infrared-sensitive video camera to perform ICGA.[10] In the year , Guyer et al. introduced the use of high resolution ( × ) digital imaging system coupled with infrared video cameras to produce better high resolution images.[17]

See also

[

edit

]

References

[

edit

]

Indocyanine Green AngiographyIndocyanine Green Angiography - Carver College of Medicine

Indocyanine green angiography